health HAL uses "default" service name

The getService() and registerAsService() methods of interface objects
now have default parameters of "default" for the service name. HALs
will not have to use any service name unless they want to register
more than one service.

Test: builds

Bug: 33844934
Change-Id: I9a1fd3ba598bf058b6212bd416ecdf90ea329539
diff --git a/healthd/healthd.cpp b/healthd/healthd.cpp
index cae6c4c..ed1971a 100644
--- a/healthd/healthd.cpp
+++ b/healthd/healthd.cpp
@@ -82,7 +82,7 @@
     // Initialize the board HAL - Equivalent of healthd_board_init(config)
     // in charger/recovery mode.
 
-    gHealth = IHealth::getService("health");
+    gHealth = IHealth::getService();
     if (gHealth == nullptr) {
         KLOG_WARNING(LOG_TAG, "unable to get HAL interface, using defaults\n");
         return;